1. Field of the Invention
The present invention relates to an automatic voltage conversion module, and more particularly, to an automatic voltage conversion module, in which a voltage of a utility power supplied to electric or electronic appliances, such as a washing machine, is changed to a voltage which can operate the appliances regardless of conditions of the utility power.
2. Background of the Related Art
In general, since either 110V or 220V AC voltage is supplied to each home, an electric part of home use electric/electronic appliance should be designed for both of the voltages. If an AC 220V should be supplied to a system designed for AC 110V, the system will be damaged, and, if an AC 110V should be supplied to a system designed for AC 221V, the system does not operate properly. Because of the above reason, a change over switch is provided to the electric part, so that the user can match to a supplied voltage for a normal operation of the appliance. However, if the user mismatches the change over switch from overlooking, the foregoing malfunction of the appliance will occur. Therefore, a device is needed that can sense an incoming voltage, and make an automatic change over. FIG. 1 illustrates a circuit of an electric part used for a related art washing machine. As respective modules in the washing machine are designed for DC 311V, the electric part should change the voltage before supply to the modules.
Referring to FIG. 1, the electric part is provided with a utility power source 1, a power switch 2 for supplying or cutting off the power to a system depending on a users selection, a bridge rectifier 3 for rectifying an AC current from the utility power 1 into a DC current, a smoother 4 having smoothing capacitors C1 and C2 and resistors R1 and R2 for smoothing the rectified current at the bridge rectifier 3 to provide a 311V DC voltage, and a motor driver 5 for receiving an output of the smoother 4 and driving a washing motor in the washing machine. The smoother 4 has two identical capacitors C1 and C2 connected in series, and two identical resistors R1 and R2 connected to the capacitors C1 and C2 in parallel, respectively.
The operation of the aforementioned related art electric part will be explained.
When the user turns on the power switch 2 for putting the washing machine into operation, the 220V AC power from the utility power source 1 is provided to the bridge rectifier 3. The bridge rectifier 3 rectifies a current as paths of the current alternates for a positive half cycle and a negative half cycle, and the rectified current is provided to the smoother 4, where the current is smoothed through the smoothing capacitors C1 and C2, to provide a DC current. In this instance, the smoothed DC current has a voltage of 2.multidot.220=311V. During the positive half cycle in the above operation, a closed circuit is formed in an order of the utility power source 1.fwdarw.the first diode D1.fwdarw.the first capacitor C1.fwdarw.the second capacitor C2.fwdarw.the third diode D3.fwdarw.the utility power source 1. And, during the negative half cycle in the above operation, a closed circuit is formed in an order of the utility power source 1.fwdarw.the fourth diode D4.fwdarw.the first capacitor C1.fwdarw.the second capacitor C2.fwdarw.the second diode D2.fwdarw.the utility power source 1. At the end, since the DC 311V is charged to the first capacitor C1 and the second capacitor C2 continuously, to supply the DC 311V to the motor driver 5 continuously, the washing motor(not shown) can make a regular operation.
However, if a 110V is supplied to the utility power source 1 in the related art electric part, the system can not be operate properly. That is, since the electric part is designed to provide the 311V only when an AC 220V is supplied, in a case when 110V is supplied to the electric part, to provide a DC voltage of 2.multidot.110=155.5V through the smoother 4, the system does not operate properly. If a change over switch is provided for solving the above problem, a separate circuit for changing an external low voltage to a high voltage before supply to the system is required.